The present invention relates to a transition metal compound as catalyst component for polymerization, a method for producing an aromatic vinyl compound type polymer employing it, a method for producing an aromatic vinyl compound polymer and an aromatic vinyl compound-olefin copolymer, having an isotactic stereoregularity, and a novel aromatic vinyl compound-olefin copolymer.
For the production of a copolymer of an olefin with an aromatic vinyl compound, such as ethylene with styrene, studies have been conducted primarily by using so-called heterogeneous Ziegler-Natta catalysts (e.g. Polymer Bulletin, 20, 237-241 (1988), Macromolecules, 24, 5476 (1991)). However, conventional heterogeneous Ziegler-Natta catalyst systems are not so practical, since the catalytic activities are low, the styrene content in the product is very low at a level of a 1 mol %, or the product does not have a uniform regular copolymer structure or contains a substantial amount of homopolymers such as polyethylene and isotactic or atactic polystyrene.
Further, the stereoregularity of the obtained polystyrene is isotactic, but in the copolymerization, no stereoregularity of an alternating structure of styrene and an olefin is observed, or an alternating structure itself is not substantially contained.
Further, some styrene-ethylene copolymers obtainable by using so-called single-site catalyst systems comprising a transition metal compound and an organoaluminum compound, and methods for their production, have been known.
JP-A-3-163088 and JP-A-7-53618 disclose styrene-ethylene copolymers where no normal styrene chain is present i.e. so-called pseudo random copolymers, obtained by using a complex having a so-called constrained geometrical structure. Here, a normal styrene chain is meant for a head-to-tail bond chain. Further, hereinafter styrene may sometimes be represented by St.
However, phenyl groups in the alternating structure of styrene-ethylene present in such pseudo random copolymers, have no stereoregularity. Further, no normal styrene chain is present, whereby the content of styrene can not exceed 50 mol %. Further, the catalytic activities are practically inadequate.
JP-A-6-49132 and Polymer Preprints, Japan, 42, 2292 (1993) disclose methods for producing similar styrene-ethylene copolymers wherein no normal St chain is present, i.e. so-called pseudo random copolymers, by using a catalyst comprising a bridged metallocene type Zr complex and a cocatalyst.
However, according to Polymer Preprints, Japan, 42, 2292 (1993), phenyl groups in the alternating structure of styrene-ethylene present in such pseudo random copolymers, have no substantial stereoregularity. Further, like in the case of a complex having a constrained geometrical structure, no normal styrene chain is present, and the styrene content can not exceed 50 mol %. The catalytic activities are also practically inadequate.
Further, it has recently been reported to produce a styrene-ethylene copolymer close to an alternating copolymer having a stereoregularity under a condition of an extremely low temperature (xe2x88x9225xc2x0 C.) by using 1,2-ethylene(xe2x80x94CH2xe2x80x94CH2xe2x80x94) bridged bisindenyl type Zr complex; rac[ethylenebis(indenyl)zirconium dichloride] (Macromol. Chem., Rapid Commun., 17, 745 (1996)).
However, from the 13Cxe2x80x94NMR spectrum disclosed, it is evident that this copolymer has no normal styrene chain. Further, if copolymerization is carried out at a polymerization temperature of at least room temperature by using this complex, only a copolymer having a low styrene content and a low molecular weight is obtainable.
On the other hand, a styrene-ethylene alternating copolymer obtainable by using a Ti complex having a substituted phenol type ligand, is known (JP-A-3-250007 and Stud. Surf. Sci. Catal., 517 (1990)). This copolymer has a feature that it consists essentially of an alternating structure of ethylene and styrene and contains substantially no other structure such as an ethylene chain, a structure comprising an ethylene chain and styrene or a structure of e.g. a head-to-head or tail-to-tail bond (hereinafter referred to as a heterogeneous bond) of styrene. The alternating index (value xcex in the present specification) of the copolymer is at least 70, substantially at least 90.
Namely, the resulting copolymer is a copolymer having a very high degree of alteration and consisting substantially solely of the alternating structure, whereby it is substantially difficult to change the compositional ratio of the copolymer consisting of 50 mol % of ethylene and 50 mol % of styrene. Further, the stereoregularity of phenyl groups is isotactic, but the isotactic diad index m is about 0.92, whereby the melting point is low at a level of from 110 to 120xc2x0 C.
Further, the weight average molecular weight is low at a level of 20,000, which is inadequate to provide practically useful physical properties as a crystalline polymer. It should also be added that the catalytic activities are very low, and the copolymer can hardly be regarded as practically useful, since it is obtained as a mixture with e.g. syndiotactic polystyrene.
It has been attempted to produce a copolymer of a propylene with styrene by means of a Solvay type Ziegler-Natta catalyst (Macromolecules, 22, 2875 (1989)). However, the catalytic activities are low, and the styrene content is at a level of 4.4 mol % at best. With respect to a single-site catalyst system comprising a transition metal compound and an organoaluminum compound, a case wherein a Ewen-type zirconium complex which is a so-called metallocene catalyst, is employed for copolymerization of propylene with styrene, is known (JP-A-8-269134). However, the styrene content of the copolymer thereby obtainable is as low as a few %, and the stereoregularity is syndiotactic.
The production of an isotactic aromatic vinyl compound polymer such as an isotactic polystyrene, has been studied by means of a so-called heterogeneous Ziegler-Natta catalyst.
For example, such a catalyst is disclosed in Macromolecules, 24, 5476 (1991), but the catalytic activities are low, and as a fate of a heterogeneous Ziegler-Natta catalyst, due to non-uniform active sites, the molecular weight distribution (Mw/Mn) tends to be as broad as at least 3, and cation polymerization and other polymerizations tend to simultaneously proceed, and a substantially a large amount of atactic polystyrene is usually produced as a by-product.
On the other hand, in the polymerization of styrene using a single-site catalyst, syndiotactic polystyrene is usually obtained. Only when a nickel-type non-metallocene complex is used, formation of isotactic polystyrene has been reported, for example, in Macromolecules, 29, 4172 (1996). However, the molecular weight, the catalytic activities and the stereoregularities are all inadequate.
In any case, no isotactic polystyrene has been obtained with a system using a metallocene complex as a catalyst component.
It is an object of the present invention to provide a metal compound for polymerization, a method for producing an aromatic vinyl compound type stereoregular polymer by using it, a method for producing an aromatic vinyl compound polymer and an aromatic vinyl compound-olefin copolymer, having isotactic stereoregularity, and a novel aromatic vinyl compound-olefin copolymer.
Firstly, the present invention provides a transition metal compound of the following formula (1) as catalyst component for the production of an aromatic vinyl compound polymer or an aromatic vinyl compound-olefin copolymer: 
wherein A is an unsubstituted or substituted benzindenyl group of the following formula K-2, K-3 or K-4: 
wherein each of R1 to R3 is hydrogen, a C1-20 alkyl group, a C6-10 aryl group, a C7-20 alkylaryl group, a halogen atom, OSiR3, SiR3 or PR2 (wherein each R is a C1-10 hydrocarbon group), provided that the plurality of R1, the plurality of R2 and the plurality of R3 may be the same or different, respectively, and each pair of adjacent R1, adjacent R2 and adjacent R3 may together, with the atoms joining them, form a 5- to 8- member aromatic or aliphatic ring,
B is an unsubstituted or substituted benzindenyl group of the same chemical formula as A, or an unsubstituted or substituted cyclopentadienyl group, an unsubstituted or substituted indenyl group or an unsubstituted or substituted fluorenyl group, of the following formula K-5, K-6 or K-7: 
wherein each of R4 to R6 is hydrogen, a C1-20 alkyl group, a C6-10 aryl group, a C7-20 alkylaryl group, a halogen atom, OSiR3, SiR3 or PR2 (wherein each R is a C1-10 hydrocarbon group), provided that the plurality of R4, the plurality of R5 and the plurality of R6 may be the same or different, respectively,
when both A and B are unsubstituted or substituted benzindenyl groups, they may be the same or different,
Y is a methylene group or a silylene group, which has bonds to A and B and which has, as substituents, hydrogen or a C1-15 hydrocarbon group, wherein the substituents may be the same or different from each other, or Y may have, together with the substituents, a cyclic structure,
X is hydrogen, a halogen atom, an alkyl group, an aryl group, an alkylaryl group, a silyl group, a methoxy group, an ethoxy group, an alkoxy group or a dialkylamide group, and
M is zirconium, hafnium or titanium.
The unsubstituted benzindenyl group may, for example, be 4,5-benz-1-indenyl (another name: benz(e)indenyl), 5,6-benz-1-indenyl, or 6,7-benz-1-indenyl, and the substituted benzindenyl group may, for example, be 4,5-naphtho-1-indenyl, 4,5-pyrene-1-indenyl, 4,5-triphenylene-1-indenyl, xcex1-acenaphtho-1-indenyl, 3-cyclopenta[c]phenanthryl or 1-cyclopenta[1]phenanthryl.
Particularly preferably, the unsubstituted benzindenyl may, for example, 4,5-benz-1-indenyl (another name: benz(e)indenyl), 5,6-benz-1-indenyl, or 6,7-benz-1-indenyl, and the substituted benzindenyl group may, for example, be xcex1-acenaphtho-1-indenyl, 3-cyclopenta[c]phenanthryl, or 1-cyclopenta[1]phenanthryl.
In the above formula (1), B is preferably the same unsubstituted or substituted benzindenyl group as above A, or an unsubstituted or substituted cyclopentadienyl group, an unsubstituted or substituted indenyl group or an unsubstituted or substituted fluorenyl group, of the following formula K-5, K-6 or K-7: 
In the above K-5 to K-7, each of R4, R5 and R6 is hydrogen, a C1-20 alkyl group, a C6-10 aryl group, a C7-20 alkylaryl group, a halogen atom, OSiR3, SiR3 or PR2 (wherein each R is a C1-10 hydrocarbon group), the plurality of R4, the plurality of R5 and the plurality of R6 may be the same or different, respectively. However, B is preferably in a racemic-form (or pseudo racemic-form) with A.
Particularly preferably, B is, as an unsubstituted benzindenyl group, 4,5-benz-1-indenyl, 5,6-benz-1-indenyl or 6,7-benz-1-indenyl, or as a substituted benzindenyl group, xcex1-acenaphtho-1-indenyl, 3-cyclopenta[c]phenanthryl, or 1-cyclopenta[1]phenanthryl, or as an unsubstituted inoenyl group, 1-indenyl, or as a substituted indenyl group, 4-phenylinoenyl or 4-naphthylindenyl.
The unsubstituted cyclopentadienyl may, for example, be cyclopentadienyl, and the substituted cyclopentadienyl may, for example, 4-aryl-1-cyclopentadienyl, 4,5-diaryl-1-cyclopentadienyl, 5-alkyl-4-aryl-1-cyclopentadienyl, 4-alkyl-5-aryl-1-cyclopentadienyl, 4,5-dialkyl-1-cyclopentadienyl, 5-trialkylsilyl-4-alkyl-1-cyclopentadienyl, or 4,5-dialkylsilyl-1-cyclopentadienyl.
The unsubstituted indenyl group may, for example, be 1-indenyl, and the substituted indenyl group may, for example, be 4-alkyl-1-indenyl, 4-aryl-1-indenyl, 4,5-dialkyl-1-indenyl, 4,6-dialkyl-1-indenyl, 5,6-dialkyl-1-indenyl, 4,5-diaryl-1-indenyl, 5-aryl-1-indenyl, 4-aryl-5-alkyl-1-indenyl, 2,6-dialkyl-4-aryl-1-indenyl, 5,6-diaryl-1-indenyl, or 4, 5, 6-triaryl-1-indenyl.
The unsubstituted fluorenyl group may, for example, be a 9-fluorenyl group, and the substituted fluorenyl group may, for example, be a 7-methyl-9-fluorenyl group or a benz-9-fluorenyl group.
In the above formula (1), Y is carbon or silicon which has bonds to A and B and which has substituents, and it is a methylene group or a silylene group having, as substituents, hydrogen or a C1-15 hydrocarbon group.
The substituents may be the same or different from each other. Further, Y may have a cyclic structure such as a cyclohexylidene group or a cyclopentylidene group.
Preferably, Y is a substituted methylene group which has bonds to A and B and which is substituted by hydrogen or a C1-15 hydrocarbon group. The hydrocarbon group may, for example, be an alkyl group, an aryl group, a cycloalkyl group or a cycloaryl group. The substituents may be the same or different from each other.
Particularly preferably, Y is xe2x80x94CH2xe2x80x94, xe2x80x94CMe2xe2x80x94, xe2x80x94CEt2xe2x80x94, xe2x80x94CPh2xe2x80x94, cyclohexylidene or cyclopentylidene. Here, Me is a methyl group, Et is an ethyl group and Ph is a phenyl group.
X is hydrogen, a halogen atom, a C1-15 alkyl group, a C6-10 aryl group, a C8-12 alkylaryl group, a silyl group having a C1-4 hydrocarbon substituent, a C1-10 alkoxy group, or a dialkylamide group having a C1-6 alkyl substituent. The halogen atom may, for example, be chlorine or bromine, the alkyl group may, for example, be a methyl group or an ethyl group, and the aryl group may, for example, be a phenyl group. The alkylaryl group may, for example, be a benzyl group, the silyl group may, for example, be trimethylsilyl, the alkoxy group may, for example, be a methoxy group, an ethoxy group or an isopropoxy group, and the dialkylamide group may, for example, be a dimethylamide group. X may be the same or different from each other, or having a bond structure between X.
Especially when X is a dimethylamide group, the transition metal catalyst component of the present invention can be produced by the method disclosed in WO95/32979, whereby there is a merit that such a catalyst component can simply and inexpensively be produced. Namely, it can be produced by a single step from a ligand compound and zirconium tetrakisdimethylamide at a temperature of at least room temperature, where control is easy. Strictly, the transition metal catalyst component produced by this process is a racemic-form containing a substantial amount of meso-form as an impurity. However, inclusion of the meso-form in the catalyst gives no substantial influence in the present invention.
In the case of a transition metal complex wherein X is chlorine, a highly costly process for reacting a dimethylamide type complex with a dimethylamine hydrochloride at a low temperature, such as xe2x88x9278xc2x0 C. is required, whereby the product will be expensive.
Further, when X is a dimethylamide, the speed for forming active species after contacting with methylalumoxane as the cocatalyst, tends to be slightly slow as compared with a case where X is chlorine. This has an important merit from the viewpoint of the production process in that particularly in a batch solution polymerization, in a polymerization method of preliminarily dissolving a cocatalyst in the polymerization solution and introducing a transition metal compound to the polymerization solution under prescribed condition to initiate the polymerization, active species are gradually formed during the polymerization, whereby abrupt generation of polymerization heat immediately after the introduction of the catalyst can be reduced, and heat removal of the polymerization liquid can be facilitated.
M is zirconium, hafnium or titanium. Particularly preferred is zirconium.
The following compounds may be mentioned as specific examples of such a transition metal compound as catalyst component.
For example, dimethylmethylene bis(4,5-benz-1-indenyl)zirconium dichloride (another name: dimethylmethylenebis(benz-e-indenyl)zirconium dichloride), di-n-propylmethlenebis(4,5-benz-1-indenyl)zirconium dichloride, di-i-propylmethylenebis(4,5-benz-1-indenyl)zirconium dichloride, cyclohexylidenebis(4,5-benz-1-indenyl)zirconium dichloride, cyclopentylidenebis(4,5-benz-1-indenyl)zirconium dichloride, diphenylmethylenebis(4,5-benz-1-indenyl)zirconiumm dichloride, dimethylmethylene(cyclopentadienyl)(4,5-benz-1-indenyl)zirconium dichloride, dimethylmethylene(1-indenyl)(4,5-benz-1-indenyl)zirconium dichloride, dimethylmethylene(1-fluorenyl)(4,5-benz-1-indenyl)zirconium dichloride, dimethylmethylene(4-phenyl-1-indenyl)(4,5-benz-1-indenyl)zirconium dichloride, dimethylmethylene(4-naphthyl-1-indenyl)(4,5-benz-1-indenyl)zirconium dichloride, dimethylmethylenebis(5,6-benz-1-indenyl)zirconium dichloride, dimethylmethylene(5,6-benz-1-indenyl)(1-indenyl)zirconium dichloride, dimethylmethylenebis(4,7-benz-1-indenyl)zirconium dichloride, dimethylmethylene(6,7-benz-1-indenyl)(1-indenyl)zirconium dichloride, dimethylmethylenebis(4,5-naphtho-1-indenyl)zirconium dichloride, dimethylmethylenebis(xcex1-acetonaphtho-1-indenyl)zirconium dichloride, dimethylmethylenebis(3-cyclopenta(c)phenanthryl)zirconium dichloride, dimethylmethylene(3-cyclopenta(c)phenanthryl)(1-indenyl)zirconium dichloride, dimethylmethylenebis(1-cyclopenta(1)phenanthryl)zirconium dichloride, dimethylmethylene(1-cyclopenta(1)phenanthryl)(1-indenyl)zirconium dichloride, dimethylmethylenebis(4,5-benz-1-indenyl)zirconium bis(dimethylamide), and dimethylmethylene(1-indenyl)(4,5-benz-1-indenyl)zirconium bis(dimethylamide), may be mentioned.
In the foregoing, zirconium complexes were exemplified, but corresponding titanium complexes and hafnium complexes may also suitably be used. Further, racemic-form or mixtures of racemic-form and meso-form may also be employed. Preferably, racemic-form or pseudo racemic-form are employed. In such a case, D-isomers or L-isomers may be employed.
The following excellent characteristics are obtainable when an aromatic vinyl compound polymer or an aromatic vinyl compound-olefin copolymer is produced by using the transition metal compound of the present invention as a polymerization catalyst component.
The catalytic activities are high, and the polymer or the copolymer can be obtained at a high productivity of a level of at least 1xc3x97108 (g/mol.transition metal catalyst) in the case where the aromatic vinyl compound content is less than 20 mol %, or at least 4.1xc3x97107 (g/mol.transition metal catalyst) when the aromatic vinyl compound content is at least 20 mol % and less than 55 mol %.
Further, it is possible to produce a random copolymer having a high aromatic vinyl compound content, particularly an aromatic vinyl compound-ethylene random copolymer wherein the aromatic vinyl compound content exceeds 55 mol %.
Especially when a polymerization catalyst comprising a transition metal compound as catalyst component having a 3-cyclopenta(c)phenanthryl group as ligand A or A and B, such as rac-dimethylmethylenebis(3-cyclopenta(c)phenanthryl)zirconium dichloride, and a cocatalyst, is employed, it is possible to produce a styrene-olefin random copolymer, particularly a styrene-ethylene random copolymer, and an isotactic polystyrene, having a high molecular weight, under very high catalytic activities. In such a case, particularly with respect to a copolymer wherein the aromatic vinyl compound content is at least 50 mol %, it is possible to produce a copolymer having a weight average molecular weight of at least 100,000, preferably 200,000. Further, the styrene-ethylene random copolymer thereby obtained, has a characteristic that it is a copolymer having a high random nature (low alternating nature) as compared with a case with the same aromatic vinyl compound content under the same polymerization condition. The isotacticity of the structure contained in the resulting polymer or copolymer is very high.
Secondly, the present invention provides a transition metal compound of the following formula (2-1) or (2xe2x80x942) as catalyst component for the production of an aromatic vinyl compound polymer or an aromatic vinyl compound-olefin copolymer: 
wherein A, B, Y, M and X are as defined with respect to the formula (1), wherein the angle (the bite angle) between metal M and the centroid of each cyclopentadienyl structure in A and B, is at most 120xc2x0.
The bite angle can be obtained by X-ray diffraction of a single crystal of the transition metal catalyst component or by the following calculation method employing a computer.
SGI Origin Work Station was employed which has IRIX6.4 mounted as an operation system and which has MIPS R10000 Processo Chip Revision 2.6 2xc3x97180 MHz IP27 processors as CPU.
The employed softwares were Molecular orbital method G94revision, E. 2, Gaussian 94 (manufactured by Gaussian Inc.) and Option (Geom, OPT, HF, DIRECT, STO-3G).
The results of the study carried out with respect to dimethylmethylene(cyclopentadienyl)(fluorenyl)zirconium dichloride are shown below, which substantiate that the method of obtaining a bite angle by such a calculation, is proper.
Bite angle obtained by the above calculation method: 119xc2x0
Bite angle obtained by single crystal X-ray diffraction method: 117.9xc2x0
Literature value: Macromol. Chem., Macromol. Symp., 48/49 , 253 (1991).
The two values substantially agree, thus substantiating that the calculation method is proper.
By variously changing the structures of A and B, bite angles were obtained by calculation, and such bite angles agreed to one another within a difference of 1xc2x0. Namely, the structures of A and B do not affect the bite angle.
The present inventors have studied the content of an aromatic vinyl compound in the aromatic vinyl compound-olefin copolymer under the same condition using various transition metal compound as catalyst components. As a result, it has been found that a very high aromatic vinyl compound content can be obtained when a transition metal catalyst component having a bite angle of at most 120xc2x0 is employed.
Such a bite angle can be accomplished when in the above formula (2-1) or (2xe2x80x942), Y is a methylene group having hydrogen or a C1-15 hydrocarbon group. In the case of the formula (2xe2x80x942), two Y may be the same or different.
Among a group of the above-mentioned transition metal catalyst components, the formula (2-1) represents a group of transition metal catalyst components in which Y is a methylene group which has bonds to A and B and which has, as substituents, hydrogen or a C1-15 hydrocarbon group.
In the case of the formula (2xe2x80x942), the following compounds may be mentioned as examples of such a transition metal catalyst component:
(1,2xe2x80x2-methylene)(2,1xe2x80x2-methylene)bis(4,5-benz-1-indenyl)zirconium dichloride, (1,2xe2x80x2-isopropylidene)(2,1xe2x80x2-isopropylidene)bis(4,5-benz-1-indenyl)zirconium dichloride, (1,2xe2x80x2-isopropylidene)(2,1xe2x80x2-methylene)bis(4,5-benz-1-indenyl)zirconium dichloride, (1,2xe2x80x2-methylene)(2,1xe2x80x2-methylene)(1-indenyl)(4,5-benz-1-indenyl)zirconium dichloride, (1,2xe2x80x2-isopropylidene)(2,1xe2x80x2-isopropylidene)(1-indenyl)(4,5-benz-1-indenyl)zirconium dichloride, (1,2xe2x80x2-isopropylidene)(2,1xe2x80x2-methylene)(1-indenyl)(4,5-benz-1-indenyl)zirconium dichloride, (1,2xe2x80x2-methylene)(2,1xe2x80x2-methylene)(cyclopentadienyl)(4,5-benz-1-indenyl)zirconium dichloride, (1,2xe2x80x2-isopropylidene)(2,1xe2x80x2-isopropylidene)(cyclopentadienyl)(4,5-benz-1-indenyl)zirconium dichloride, (1,2xe2x80x2-isopropylidene)(2,1xe2x80x2-methylene)(cyclopentadienyl)(4,5-benz-1-indenyl)zirconium dichloride, (1,2xe2x80x2-methylene)(2,1xe2x80x2-methylene)bis(3-cyclopenta(c)phenanthryl)zirconium dichloride, (1,2xe2x80x2-isopropylidene)(2,1xe2x80x2-isopropylidene)bis(3-cyclopenta(c)phenanthryl)zirconium dichloride, (1,2xe2x80x2-isopropylidene)(2,1xe2x80x2-methylene)bis(3-cyclopenta(c)phenanthryl)zirconium dichloride, (1,2xe2x80x2-methylene)(2,1xe2x80x2-methylene)bis(1-cyclopenta(1)phenanthryl)zirconium dichloride, (1,2xe2x80x2-isopropylidene)(2,1xe2x80x2-isopropylidene)bis(1-cyclopenta(1)phenanthryl)zirconium dichloride, and (1,2xe2x80x2-isopropylidene)(2,1xe2x80x2-methylene)bis(1-cyclopenta(1)phenanthryl)zirconium dichloride.
In the foregoing, zirconium complexes were exemplified, but corresponding titanium complexes and hafnium complexes may also suitably be used.
As such transition metal compound as catalyst components, racemic-form or pseudo racemic-form are preferably used. In such a case, D-isomers or L-isomers may be used. Further, a mixture of a racemic-form and a meso-form may also be used.
Thirdly, the present invention provides a polymerization catalyst for producing an aromatic vinyl compound polymer or an aromatic vinyl compound-olefin copolymer, which comprises such a transition metal compound and a cocatalyst and which provides a remarkably high productivity, and an efficient method for producing an aromatic vinyl compound polymer and an aromatic vinyl compound-olefin copolymer, employing such a catalyst.
Particularly, it provides a polymerization catalyst for producing an aromatic vinyl compound polymer having isotactic stereoregularity in the polymer structure or an aromatic vinyl compound-olefin copolymer having an isotactic structure, and a method for producing an isotactic aromatic vinyl compound polymer and an aromatic vinyl compound-olefin copolymer having an isotactic structure, employing such a catalyst.
As the cocatalyst to be used in the present invention, a cocatalyst which has been used in combination with a transition metal compound as catalyst component, can be used. As such a cocatalyst, aluminoxane (or alumoxane), or a boron compound, is preferably employed.
Further, the present invention provides a method for producing an aromatic vinyl compound polymer or an aromatic vinyl compound-olefin copolymer wherein the cocatalyst to be used is an aluminoxane (or alumoxane) of the following formula (3) or (4): 
wherein R is a C1-5 alkyl group, a C6-10 aryl group or hydrogen, m is an integer of from 2 to 100, and the plurality of R may be the same or different, 
wherein Rxe2x80x2 is a C1-5 alkyl group, a C6-10 aryl group or hydrogen, n is an integer of from 2 to 100, and the plurality of Rxe2x80x2 may be the same or different.
As the aluminoxane, methylalumoxane, ethylalumoxane or triisobutylalumoxane, is preferably employed. Particularly preferred is methylalumoxane. If necessary, a mixture of these different types of alumoxanes, may be employed. Further, such an alumoxane may be used in combination with an alkylaluminum such as trimethylaluminum, triethylaluminum or triisobutylaluminum, or with a halogen-containing alkylaluminum such as dimethylaluminum chloride.
Addition of an alkylaluminum to the catalyst is effective for removing substances which hinder polymerization, such as a polymerization inhibitor in styrene, or moisture in the solvent, or for removing adverse effects against the polymerization reaction.
However, it is not necessarily required to add an alkylaluminum, if the amount of styrene, solvent, etc. is preliminarily reduced to a level not to influence the polymerization, by a known method such as distillation, bubbling with a dry inert gas or passing through a molecular sieve, or by increasing the amount of alumoxane to some extent or adding alumoxane in divided portions.
In the present invention, a boron compound may be used as a cocatalyst together with the above transition metal compound as catalyst component.
The boron compound to be used as a cocatalyst may, for example, be
triphenylcarbeniumtetrakis(pentafluorophenyl) borate {trityltetrakis(pentafluorophenyl)borate}, lithium tetra(pentafluorophenyl)borate, tri(pentafluorophenyl)boran, trimethylammoniumtetraphenyl borate, triethylammoniumtetraphenyl borate, tripropylammoniumtetraphenyl borate, tri(n-butyl)ammoniumtetraphenyl borate, tri(n-butyl)ammoniumtetra(p-tolyl)phenyl borate, tri(n-butyl)ammoniumtetra(p-ethylphenyl)borate, tri(n-butyl) ammoniumtetra (pentafluorophenyl) borate, trimethylammoniumtetra (p-tolyl) borate, trimethylammoniumtetrakis-3,5-tetramethyl phenyl borate, triethylammoniumtetrakis-3,5-dimethylphenyl borate, tributylammoniumtetrakis-3,5-dimethylphenyl borate, tributylammoniumtetrakis-2,4-dimethylphenyl borate, aniliumtetrakispentafluorophenyl borate, N,Nxe2x80x2-dimethylaniliumtetraphenyl borate, N,Nxe2x80x2-dimethylaniliumtetrakis(p-tolyl)borate, N,Nxe2x80x2-dimethylaniliumtetrakis(m-tolyl)borate, N,Nxe2x80x2-dimethylaniliumterakis(2,4-dimethylphenyl)borate, N,Nxe2x80x2-dimethylaniliumtetrakis(3,5-dimethylphenyl)borate, N,Nxe2x80x2-dimethylaniliumtetrakis(pentafluorophenyl)borate, N,Nxe2x80x2-diethylaniliumtetrakis(pentafluorophenyl)borate, N,Nxe2x80x2-2,4,5-pentamethylaniliumtetraphenyl borate, N,Nxe2x80x2-2,4,5-pentaethylaniliumtetrraphenyl borate, di-(isopropyl)ammoniumtetrakispentafluorophenyl borate, di-cyclohexylammoniumtetraphenyl borate, triphenylphosphoniumtetraphenyl borate, tri(methylphenyl)phosphoniumtetraphenyl borate, tri(dimethylphenyl)phosphoniumtetraphenyl borate, triphenylcarbeniumtetrakis (p-tolyl) borate, triphenylcarbeniumtetrakis(m-tolyl)borate, triphenylcarbeniumtetrakis(2,4-dimethylphenyl)borate, triphenylcarbeniumtetrakis(3,5-dimethylphenyl)borate, tropiliumtetrakispentafluorophenyl borate, tropiliumtetrakis (p-tolyl)borate, tropiliumtetrakis(m-tolyl)borate, tropiliumtetrakis(2,4-dimethylphenyl)borate or tropiliumtetrakis(3,5-dimethylphenyl)borate.
Such a boron compound and the above-mentioned organoaluminum compound may be used at the same time.
Especially when a boron compound is used as a cocatalyst, addition of an alkylaluminum compound such as triisobutylaluminum is effective for the removal of impurities which adversely affect the polymerization, such as water contained in the polymerization system.
Aromatic vinyl compounds to be used in the present invention may, for example, be styrene and various substituted styrenes such as p-methylstyrene, m-methylstyrene, o-methylstyrene, o-t-butylstyrene, p-t-butylstyrene, p-chlorostyrene, o-chlorostyrene, and xcex1-methylstyrene. Further, a compound having a plurality of vinyl groups in one molecule, such as divinylbenzene, may also be mentioned.
Industrially preferably, styrene, p-methylstyrene or p-chlorostyrene is used. Particularly preferably, styrene is used.
Further, as olefins to be used in the present invention, C2-20xcex1-olefins such as ethylene, propylene, 1-butene, 1-hexene, 1-methyl-1-pentene, 1-octene and cyclic olefins such as cyclopentene, norbornene and norbonadiene, may be mentioned. These olefins may be used alone or in combination as a mixture of two or more of them. As such olefins, ethylene and propylene are preferred. In the following description, examples in which ethylene and propylene are used as olefins, will be referred to.
For the production of a polymer or a copolymer of the present invention, the olefin, the above exemplified aromatic vinyl compound, the transition metal compound as catalyst component as a metal complex and the cocatalyst are contacted. As to the manner and order for contacting, an optional known method may be employed.
For the production of an aromatic vinyl compound polymer of the present invention, the above exemplified aromatic vinyl compound, the transition metal compound as catalyst component as a metal complex and the cocatalyst are contacted. As to the manner and order for contacting, an optional known method may be employed.
As a method for the above polymerization or copolymerization, it is possible to employ a method for carrying out the polymerization in a liquid monomer without using any solvent, or a method of using a single solvent or a mixed solvent selected from saturated aliphatic or aromatic hydrocarbons or halogenated hydrocarbons, such as pentane, hexane, heptane, cyclohexane, benzene, toluene, ethylbenzene, xylene, chlorobenzene, chlorotoluene, methylene chloride or chloroform. If necessary, batch polymerization, continuous polymerization, stepwise polymerization, slurry polymerization, preliminary polymerization or gas phase polymerization may be employed.
Heretofore, when styrene is employed as a monomer component, it used to be impossible to employ gas phase polymerization in view of its low vapor pressure. However, when a catalyst of the present invention comprising a transition metal compound as catalyst component for polymerization and a cocatalyst, is employed, the copolymerization ability of styrene will be remarkably high, whereby copolymerization is possible even at a low styrene monomer concentration. Namely, copolymerization of an olefin with styrene is possible even under a low styrene partial pressure under a gas phase polymerization condition. In such a case, the transition metal catalyst component for polymerization and the cocatalyst may be used as supported on a suitable known carrier.
The polymerization or copolymerization temperature is suitably from xe2x88x9278xc2x0 C. to 200xc2x0 C. A polymerization temperature lower than xe2x88x9278xc2x0 C. is industrially disadvantageous, and if the temperature exceeds 200xc2x0 C., decomposition of the metal complex is likely to take place, such being undesirable. Industrially more preferably, the temperature is from xe2x88x9220 to 160xc2x0 C., particularly from 30 to 160xc2x0 C.
The pressure for copolymerization is suitably from 0.1 to 200 atm, preferably from 1 to 50 atm, industrially particularly preferably, from 1 to 30 atm.
When an organoaluminum compound is used as a cocatalyst, it is preferably used in an aluminum atom/complex metal atom ratio of from 0.1 to 100,000, preferably from 10 to 10,000, relative to the metal of the complex. If the ratio is smaller than 0.1, the metal complex can not effectively be activated, and if it exceeds 100,000, such will be economically disadvantageous.
When a boron compound is used as a cocatalyst, it is used in an atomic ratio of boron atom/complex metal atom of from 0.01 to 100, preferably from 0.1 to 10, particularly preferably 1. If the atomic ratio is less than 0.01, the metal complex can not effectively be activated, and if it exceeds 100, such is economically disadvantageous.
The metal complex and the cocatalyst may be prepared by mixing them outside the polymerization tank, or they may be mixed in the tank during polymerization.
Fourthly, the present invention provides an aromatic vinyl compound-olefin copolymer obtained by using the transition metal compound as catalyst component of the present invention or by the method of the present invention.
Further, it provides an aromatic vinyl compound-ethylene random copolymer having a head-to-tail chain structure of at least two aromatic vinyl compound units, wherein the aromatic vinyl compound content is from 5 to 99.9 mol %. This copolymer is a novel copolymer and includes an aromatic vinyl compound-ethylene random copolymer obtained by using the transition metal compound as catalyst component of the present invention or by the method of the present invention. However, it is not particularly limited by the transition metal catalyst component or the method of the present invention.
In the following, reference is made to a styrene-ethylene random copolymer as an example of the aromatic vinyl compound-ethylene random copolymer of the present invention. However, the present invention is by no means restricted to such a styrene-ethylene copolymer.
The structure is determined by a nuclear magnetic resonance method (NMR).
The copolymer of the present invention has main peaks at the following positions in 13C-NMR using TMS as standard.
Namely, it shows peaks attributable to the main chain methylene and the main chain methine carbon in the vicinity of from 24 to 25 ppm, 27 ppm, 30 ppm, from 34 to 37 ppm, from 40 to 41 ppm and from 42 to 46 ppm, peaks attributable to five atoms not bonded to the polymer chain among phenyl groups in the vicinity of 126 ppm and 128 ppm, and a peak attributable to one carbon bonded to the polymer main chain among phenyl groups in the vicinity of 146 ppm.
The styrene-ethylene random copolymer of the present invention is a styrene-ethylene random copolymer having a styrene content of at least 5 and less than 99.9%, more preferably at least 10 and less than 99.9%, by molar fraction, and the stereoregularity of phenyl groups in the alternating structure of styrene and ethylene of the following formula (5) contained in its structure is represented by an isotactic diad index m of larger than 0.75, and the alternating structure index xcex of the following formula (i) is smaller than 70 and larger than 1, preferably smaller than 70 and larger than 5:
xcex=A3/A2xc3x97100xe2x80x83xe2x80x83(i)
Here, A3 is the sum of areas of three peaks a, b and c attributable to the carbons in styrene-ethylene alternating structure of the following formula (5xe2x80x2). Further, A2 is the sum of areas of peaks attributable to the main chain methylene and the main chain methine carbon, as observed within a range of from 0 to 50 ppm by 13C-NMR using TMS as standard: 
wherein Ph is an aromatic group such as a phenyl group, and x is an integer of at least 2, representing the number of repeating units, 
wherein Ph is an aromatic group such as a phenyl group, and x is an integer of at least 2, representing the number of repeating units.
In the styrene-ethylene random copolymer of the present invention, the stereoregularity of phenyl groups in the alternating copolymer structure of ethylene and styrene being an isotactic structure is meant for a structure wherein the isotactic diad index m (or a meso diad fraction) is more than 0.75, preferably more than 0.85, more preferably more than 0.95.
The isotactic diad index m of the alternating copolymer structure of ethylene and styrene can be obtained by the following formula (ii) from an area Ar of the peak attributable to the r structure and an area Am of the peak attributable to the m structure appearing in the vicinity of 25 ppm.
m=Am/(Ar+Am)xe2x80x83xe2x80x83(ii)
The positions of the peaks may sometimes shift more or less depending upon the measuring conditions or the solvent used.
For example, when chloroform-d is used as a solvent, and TMS is used as standard, the peak attributable to the r structure appears in the vicinity of from 25.4 to 25.5 ppm, and the peak attributable to the m structure appears in the vicinity of from 25.2 to 25.3 ppm.
Further, when 1, 1, 2, 2-tetrachloroethane-d2 is used as a solvent, and the center peak (shift value of 73.89 ppm from TMS standard) of the triplet of the 1, 1, 2, 2-tetrachloroethane-d2 is used as standard, the peak attributable to the r structure appears in the vicinity of from 25.3 to 25.4 ppm, and the peak attributable to the m structure appears in the vicinity of from 25.1 to 25.2 ppm.
Here, the m structure represents a meso diad structure, and the r structure represents a racemic diad structure.
In the styrene-ethylene random copolymer of the present invention, a peak attributable to the r structure of the alternating structure of ethylene and styrene is not substantially observed.
The chain structure of a head-to-tail bond of styrene units contained in the styrene-ethylene random copolymer of the present invention is a chain structure of at least two styrenes, preferably a chain structure of at least three styrenes, which can be represented by the following structure: 
wherein n is an optional integer of at least 2, and Ph is aromatic group such as phenyl group.
The chain structure wherein two styrene units are bonded head-to-tail, gives peaks in the vicinity of from 42.4 to 43.0 ppm and from 43.7 to 44.5 ppm in the 13C-NMR measurement using TMS as standard and 1,1,2,2-tetrachloroethane-d2 as a solvent.
The chain structure in which at least three styrene units are bonded head-to-tail gives peaks also in the vicinity of from 40.7 to 41.0 ppm and from 43.0 to 43.6 ppm in a similar measurement. Accordingly, the chain structure in which at least two styrene units bonded head-to-tail gives a peak in the vicinity of from 40 to 45 ppm in a similar measurement.
On the other hand, in the conventional so-called pseudo random copolymer, no head-to-tail chain structure of styrene can be found even in the vicinity of 50 mol % at which the styrene content is maximum. Further, even if homopolymerization of styrene is attempted by using a catalyst for the preparation of a pseudo random copolymer, no polymer is obtainable. Depending upon e.g. the polymerization condition, an extremely small amount of an atarctic styrene homopolymer may sometimes be obtained. However, this is considered to have been formed by radical polymerization or cation polymerization by coexisting methylalumoxane or an alkylaluminum included therein.
Further, in the styrene-ethylene random copolymer of the present invention, the stereoregularity of phenyl groups in the head to tail chain structure of styrene units is isotactic.
The stereoregularity of phenyl groups in the head to tail chain structure of styrene units being isotactic, is meant for a structure wherein the isotactic diad index ms (or a meso diad fraction) is larger than 0.5, preferably at least 0.7, more preferably at least 0.8.
The stereoregularity of the chain structure of styrene units is determined by the peak position of methylene carbon in the vicinity of from 43 to 44 ppm as observed by 13C-NMR and by the peak position of the main chain proton as observed by 1H-HMR.
According to U.S. Pat. No. 5,502,133, methylene carbon of an isotactic polystyrene chain structure appears in the vicinity of from 42.9 to 43.3 ppm, but methylene carbon of a syndiotactic polystyrene chain structure appears in the vicinity of from 44.0 to 44.7 ppm. The positions of the sharp peak of methylene carbon of the syndiotactic polystyrene and the broad peak at from 43 to 45 ppm of an atarctic polystyrene are close to or overlap the positions of peaks with relatively low intensity of other carbon of the styrene-ethylene random copolymer of the present invention. However, in the present invention, a strong methylene carbon peak is observed from 42.9 to 43.4 ppm, but no clear peak is observed in the vicinity of from 44.0 to 44.7.
Further, according to U.S. Pat. No. 5,502,133 and the Comparative Examples of the present invention, the peaks attributable to the main chain methylene and methine proton in 1H-NMR, are observed at from 1.5 to 1.6 ppm and from 2.2 to 2.3 ppm in the case of an isotactic polystyrene and at from 1.3 to 1.4 ppm and from 1.8 to 1.9 ppm in the case of a syndiotactic polystyrene.
With the copolymer of the present invention, peaks are observed at from 1.5 to 1.6 ppm and at 2.2 ppm, and the result of this NMR analysis indicates that the styrene chain in the copolymer of the present invention has isotactic stereoregularity.
The isotactic diad index ms of the chain structure of styrene units can be obtained by the following formula from the respective peaks of methylene carbon in the styrene chain structure by the 13C-NMR measurement or the main chain methylene and methine proton by the 1H-NMR measurement.
Namely, it can be obtained by the following formula (iii) from an area Arxe2x80x2 of the peak attributable to the syndiotactic diad structure (r structure) of each peak and an area Amxe2x80x2 of the peak attributable to the isotactic diad structure (m structure).
ms=Amxe2x80x2/(Arxe2x80x2+Amxe2x80x2)xe2x80x83xe2x80x83(iii)
The positions of the peaks may sometimes shift more or less depending upon the measuring conditions or the solvent used.
The random copolymer in the present invention is a copolymer containing a chain structure wherein styrene units are bonded head-to-tail, a chain structure wherein ethylene units are bonded to one another and a structure in which styrene units and ethylene units are bonded. The proportions of these structures contained in the copolymer vary depending upon the content of styrene or polymerization conditions such as the polymerization temperature.
As the styrene content decreases, the proportion of the chain structure in which styrene units are bonded head-to-tail, decreases. For example, in a case of a copolymer wherein the styrene content is not higher than about 20 mol %, it is difficult to directly observe a peak attributable to the chain structure wherein styrene units are bonded head-to-tail, by the usual 13C-NMR measurement. However, it is evident that the chain structure in which styrene units are bonded head-to-tail, is present in the copolymer, although the amount may be small, even if the styrene content is not higher than 20 mol %, since it is possible to produce a homopolymer having stereoregularity under high catalytic activity by homopolymerization of styrene by using the transition metal catalyst component of the present invention or by the method of the present invention, i.e. it is essentially possible to form a chain structure in which styrene units are bonded head-to-tail, and since in the copolymer, the proportion of the chain structure in which styrene units are bonded head-to-tail, continuously changes corresponding to the styrene content of from 20 to 99 mol % at least by the 13C-NMR method. It is possible to observe the chain structure wherein styrene units are bonded head-to-tail, in the copolymer having a styrene content of not higher than 20 mol %, by such a means as the 13C-NMR analysis using a styrene monomer enriched with 13C.
The same applies to the chain structure of ethylene units.
It is known that peaks of methylene carbon of the structure derived from inversion of styrene in a conventional pseudo random copolymer having no stereoregularity, are present in two regions of from 34.0 to 34.5 ppm and from 34.5 to 35.2 ppm (for example, Polymer Preprints, Japan, 42, 2292 (1993)).
With the styrene-ethylene random copolymer of the present invention, a peak attributable to methylene carbon of an inversion bond structure derived from styrene is observed in a region of from 34.5 to 35.2 ppm, but no substantial peak is observed at from 34.0 to 34.5 ppm.
This indicates one of the characteristics of the copolymer of the present invention and indicates that high stereoregularity of phenyl groups is maintained even with an inversion bond structure of the following formula derived from styrene. 
The weight average molecular weight of the styrene-ethylene random copolymer of the present invention is at least 60,000, preferably at least 80,000, particularly preferably at least 180,000, when the styrene content is at least 5 mol % and less than 20 mol %, and at least 30,000, preferably at least 40,000, more preferably at least 100,000, particularly preferably at least 220,000, when the styrene content is at least 20 mol % and less than 55 mol %, and at least 30,000, preferably at least 40,000, when the styrene content is at least 55 mol % and at most 99.9 mol %, thus being a practical high molecular weight. The molecular weight distribution (Mw/Mn) is at most 6, preferably at most 4, particularly preferably at most 3.
Here, the weight average molecular weight is a molecular weight as calculated as polystyrene, obtained by GPC using standard polystyrene. The same applies in the following description.
The styrene-ethylene random copolymer of the present invention is characterized in that it has a highly stereoregular alternating structure of ethylene and styrene in combination with various structures such as ethylene chains having various lengths, inversion of styrene and head to tail chains of styrene having various length. Further, with the styrene-ethylene random copolymer of the present invention, the proportion of the alternating structure can be variously changed by the styrene content in the copolymer within a range of xcex of the above formula being more than 1 and less than 70. The stereoregular alternating structure is a crystallizable structure. Accordingly, the copolymer of the present invention can be made to have various properties in the form of a polymer having a crystalline, non-crystalline, or partially or microcrystalline structure, by controlling the St content or the crystallinity by a suitable method. The value xcex being less than 70 is important in order to impart significant toughness and transparency to a crystalline polymer, or to obtain a partially crystalline polymer, or to obtain a non-crystalline polymer.
As compared with a conventional styrene-ethylene copolymer having no stereoregularity or no styrene chains, the copolymer of the present invention is improved in various properties such as the initial tensile modulus, hardness, breaking strength and solvent resistance in various St content regions at various degrees of crystallinity and thus exhibits characteristic physical properties as a novel crystalline resin, a thermoplastic elastomer or a transparent soft resin.
Further, by changing the styrene content, the glass transition point can be changed within a wide range from xe2x88x9250xc2x0 C. to 100xc2x0 C.
Among copolymers of the present invention, a copolymer consisting mainly of a chain structure of styrene units and an alternating structure of styrene units and ethylene units and having a styrene content of more than 50 mol %, has high transparency and a high glass transition temperature and exhibits a high initial tensile modulus and excellent physical properties as a plastic, since ethylene chains are little or very little. Further, the alternating structure and a small amount of ethylene chains are relatively uniformly present in the chain structure, whereby the copolymer is excellent in impact resistance and shows excellent toughness. Within a styrene content from 10 mol % to 75 mol %, preferably from 15 mol % to 60 mol %, the copolymer has crystallizability due to the stereoregularity of the alternating structure and will be a copolymer having a partially or microcrystalline structure, whereby it is capable of exhibiting physical properties as a thermoplastic elastomer in the vicinity of the glass transition temperature or at a higher temperature. Further, the styrene chain structure has an isotactic stereoregularity, whereby the copolymer is crystallizable, and can be crystallized by a common crystallization treatment.
The styrene-ethylene random copolymer of the present invention can have a melting point of from about 50 to 130xc2x0 C. (by DSC) within a range of a styrene content of from 10 to 75 mol %. Further, at a styrene content of at least 90 mol %, it may have a melting point of from about 100 to 240xc2x0 C. attributable to an isotactic polystyrene chain structure. The heat of crystal fusion is at a level of from 1 to 50 J/g in either case. Such heat of crystal fusion and melting point by DSC can be changed to some extent by e.g. pretreatment conditions.
On the other hand, a conventional styrene-ethylene copolymer (a pseudo random copolymer) having no stereoregularity or no styrene chain, has a crystal structure similar to polyethylene at a low styrene content, as shown in literature ANTEC, 1634 (1996), but with an increase of the styrene content in the copolymer, the melting point and the crystallinity will rapidly decrease, and at a styrene content of about 15 mol %, the melting point becomes as low as about room temperature. Further, at a styrene content of from about 15 or 20 mol % to less than 50 mol %, the copolymer will be amorphous having no melting point.
The styrene-ethylene random copolymer of the present invention which contains basically no dissolvable plasticizer or halogen, has a basic characteristic that it is highly safe.
Further, depending upon the polymerization conditions, etc., a small amount of an atarctic homopolymer formed by polymerization of an aromatic vinyl compound by heat, radical or cation polymerization, may sometimes be contained, but such an amount should be less than 10 wt % of the total. Such a homopolymer can be removed by extraction with a solvent, but the copolymer may be used as it contains such a homopolymer, provided that there will be no particular problem from the viewpoint of the physical properties.
The copolymer of the present invention has the following characteristics at the respective styrene contents.
The copolymer with a styrene content of from 5 to 10 mol % has high tensile strength and transparency, is flexible and shows a nature as a platomer or elastomer.
The copolymer with a styrene content of from 10 to 25 mol % has high tensile strength, elongation, transparency, flexibility and resiliency and shows a nature as an elastomer.
The copolymers having the foregoing compositions are useful alone or in the form of an alloy of the copolymers having different styrene contents or in the form of an alloy with a polyolefin such as polypropylene, as a stretch film for packaging.
The copolymer with a styrene content of from 50 to 99.9 mol % having a microcrystalline structure or a low crystallinity, is a plastic having high transparency and has a high shrinking property at a temperature of at least the glass transition point and high dimensional stability at a temperature of not higher than the glass transition temperature, and thus it is useful as a shrinkable film for packaging.
Further, even if a fixed shape formed by once heating at a temperature higher than the melting point and then quenching to a temperature below the glass transition temperature, is deformed under a temperature condition of higher than the glass transition temperature and lower than the melting point and cooled to a temperature lower than the glass transition temperature to fix the deformed shape, if it is heated again to a temperature higher than the glass transition temperature and lower than the melting point, it recovers the initial shape. Namely, the copolymer has a shape memory property.
The copolymer with a styrene content of from 5 to 50 mol % is suitably employed for various applications as a substitute for soft polyvinyl chloride, in the form of an alloy with a polyolefin such as polypropylene or polyethylene, or with polystyrene or other resin, or in the form of a partially crosslinked composition. Further, the copolymer with this composition is useful as a compatibilizing agent for a polyolefin and a styrene resin, as an additive to a styrene resin or a polyolefin resin, as a modifier for rubber, as a component for an adhesive, or as bitumen (an additive to asphalt).
By changing the styrene content, the glass transition point of the copolymer of the present invention can be optionally changed within a range of from xe2x88x9250 to 100xc2x0 C., and the copolymer has a large tanxcex4 peak in the viscoelasticity spectrum and thus is useful as a vibration preventing material effective for a wide temperature range.
With the copolymer having a styrene content of about 50 mol %, it is relatively easy to increase the crystallinity as compared with copolymers with other ranges of the styrene content, and it exhibits a high initial elastic modulus although it is opaque, and thus is useful as a novel partially crystalline plastic.
As a means for increasing the crystallinity, it is possible to adopt a means such as annealing, addition of a nucleating agent or alloying with a polymer having low Tg (such as wax).
In the foregoing, a styrene-ethylene random copolymer has been described as a typical example of the aromatic vinyl compound-ethylene random copolymer of the present invention. However, the above description is generally applicable to the aromatic vinyl compound-ethylene random copolymer employing the above aromatic vinyl compound.
The present invention also provides an aromatic vinyl compound-propylene random copolymer wherein the aromatic vinyl compound content is from 5 to 99.9 mol %. This copolymer is a novel copolymer and includes an aromatic vinyl compound-propylene random copolymer obtained by using the transition metal compound as catalyst component of the present invention, or by the method of the present invention. However, such a copolymer is not restricted by the transition metal compound or the method of the present invention.
Now, a styrene-propylene random copolymer will be described as an example of the copolymer of the present invention.
The styrene-propylene random copolymer in the present invention is a copolymer having an aromatic vinyl compound content of from 5 to 99.9 mol %.
Further, it is an aromatic vinyl compound-propylene random copolymer characterized in that it has both chain structures of aromatic vinyl compound units and propylene units.
Further, it is an aromatic vinyl compound-propylene random copolymer, wherein the stereoregularity of the chain structures of the aromatic vinyl compound units and/or the propylene units, is isotactic.
The aromatic vinyl compound-olefin random copolymer of the present invention has a weight average molecular weight of at least 1,000, preferably at least 10,000, taking into consideration the physical properties as a copolymer (aromatic vinyl compound-ethylene random copolymer, is as described above). The molecular weight distribution(Mw/Mn) is at most 6, preferably at most 4, particularly preferably at most 3.
The aromatic vinyl compound-olefin random copolymer of the present invention is not necessarily required to be a pure copolymer, and other structures may be contained, or any other monomer among the above-mentioned xcex1-olefins, aromatic vinyl compounds, and conjugated dienes such as butadiene, may be copolymerized, so long as the structure and the stereoregularity are within the above-mentioned ranges.
Further, depending upon the polymerization conditions, etc., a small amount of an atarctic homopolymer formed by polymerization of an aromatic vinyl compound by heat, radical or cation polymerization, may sometimes be contained, but such an amount should be less than 10 wt % of the total. Such a homopolymer can be removed by extraction with a solvent, but the copolymer may be used as it contains such a homopolymer, provided that there will be no particular problem from the viewpoint of the physical properties.
Further, for the purpose of improving the physical properties, it may be blended with other polymers. Further, copolymers of the present invention having different styrene contents may be blended.
Fifthly, the present invention provides a method for producing an aromatic vinyl compound polymer employing a transition metal compound of the above-mentioned formula (1) and cocatalyst.
The stereoregularity of the aromatic vinyl compound polymer obtained by the method of the present invention is represented by an isotactic pentad index (mmmm) of at least 0.70, preferably at least 0.80, more preferably at least 0.90. The isotactic diad index can be obtained from a peak attributable to carbon (PhCl) of a phenyl group bonded to the main chain of the polymer in the 13C-NMR measurement.
Namely, it is obtained from the proportion of the PhCl carbon peak area attributable to the mmmm structure in the total of PhCl carbon peak areas. The PhCl carbon peak attributable to the mmmm structure appears in the vicinity of 146.3 ppm when 1, 1, 2, 2-tetrachloroethane-d2 is used as a solvent, and the triplet center peak (73.89 ppm) of 1, 1, 2, 2-tetrachloroethane-d2 is used as standard.
The isotactic aromatic vinyl compound polymer obtained in the present invention has a weight average molecular weight of at least 1,000, preferably at least 10,000 taking into consideration the physical properties as a crystalline polymer. The molecular weight distribution (Mw/Mn) is at most 6, preferably at most 4, particularly preferably at most 3.
By the method of the present invention, it is possible to obtain an isotactic aromatic vinyl compound polymer having a high stereoregularity under high catalytic activities with little formation of atactic polystyrene as a by product.
Sixthly, the present invention provides an aromatic vinyl compound-olefin alternating copolymer, preferably an aromatic vinyl compound-ethylene alternating copolymer, consisting mainly of an alternating structure. This copolymer can be obtained by using the transition metal compound as catalyst component of the present invention, or by the method of the present invention.
The aromatic vinyl compound-ethylene alternating copolymer obtainable by the present invention, is an aromatic vinyl compound-ethylene alternating copolymer characterized in that the stereoregularity of phenyl groups in the alternating structure of ethylene and an aromatic vinyl compound, is represented by an isotactic diad index m which is at least 0.95, and the alternating structure index xcex given by the above formula (i) is at least 70.
The isotactic diad (meso diad) index m of the alternating structure of ethylene and styrene in this copolymer, as an example of the aromatic vinyl compound-ethylene alternating copolymer of the present invention, can be obtained by the above-mentioned method employing the above formula (ii).
The weight average molecular weight obtained as calculated as standard polystyrene, of the aromatic vinyl compound-ethylene alternating copolymer of the present invention, is preferably at least 10,000, taking into consideration the physical properties as a crystalline plastic. The molecular weight distribution (Mw/Mn) is at most 6, preferably at most 4, particularly preferably at most 3.
This copolymer has an aromatic vinyl compound content of from 46 to 54 mol % and consists mainly of an alternating structure of ethylene and the aromatic vinyl compound, which has high stereoregularity. It is characterized in that it further contains small amounts of various structures, such as ethylene chains of various lengths, heterogeneous bonds of the aromatic vinyl compound and chains of the aromatic vinyl compound, in a proportion not higher than a certain level.
The copolymer of the present invention has a high proportion of the alternating structure and high stereoregularity due to the alternating structure and accordingly has characteristics such as high crystallinity, high melting point and a high crystallization speed.
The melting point of the copolymer obtainable by the DSC measurement is at least 130xc2x0 C. and less than 210xc2x0 C. preferably at least 150xc2x0 C. and less than 210xc2x0 C.
The copolymer of the present invention is capable of exhibiting high physical properties as a crystalline or partially crystalline polymer. Therefore, it is expected to open up a novel application of a crystalline plastic as a substitute for polypropylene, a PET resin, nylon, etc.
For the production of the alternating copolymer of the present invention, the polymerization temperature is usually from xe2x88x9220 to +40xc2x0 C.
Now, the present invention will be described in further detail with reference to Examples. However, it should be understood that the present invention is by no means restricted to such specific Examples.
In the following description, Cp represents a cyclopentadienyl group, Ind a 1-indenyl group, BInd a 4,5-benz-1-indenyl group, Flu a 9-fluorenyl group, Me a methyl group, Et an ethyl group, tBu a tertiary butyl group, and Ph a phenyl group.